Conventional paper trays used in standard 12-lead ECG (electrocardiograph) machines are generally of two types. The first is a stationary type, where the paper tray structure is a closed chamber within the recorder. A4 paper or letter paper is loaded into the paper tray from the door of the paper tray after the door is opened. The paper tray in such arrangement occupies a small space inside the ECG machine, but it is inconvenient for a user to load paper. The second is a drawer type, where the paper tray and the door are fixed and are one unit. When the door is opened, the paper tray is drawn out simultaneously. This is more convenient for loading paper, but the paper tray in such arrangement occupies a larger space inside the ECG machine, so the machine must be wider. A wider ECG machine is usually set on a trolley, but it is not conducive for printing reports and is not convenient for viewing the printed waveform. Many ECG machines sold in the market have drawer-type paper trays. When using A4 paper for printing, the width of the ECG machine must be over 400 millimeters, which makes it inconvenient to use.
Thus, conventional paper trays for 12-lead ECG machines sold in the market have two disadvantages: (1) when a stationary-type paper tray is used, it is difficult to load paper; and (2) when a drawer-type paper tray is used, the ECG machine must be wider, making it less convenient to use.